1. Field of the Invention
The present invention relates to a retaining wall and soil reinforcement subsystem, and to an improved construction element for use therein.
2. Brief Description of Related Art
Retaining walls are presently used in a wide variety of architectural and site development applications including, for example, office developments, commercial complexes, industrial sites, residential developments, waterfront and coastal structures, and highway cut and fill areas. In such applications, it is not uncommon for the height of retaining walls to exceed 20 feet or more. In nearly all applications, such retaining walls must provide stability against pressures exerted by back fill soil and heavy surcharge loads.
One popular retaining wall system is commercially available from the Tensar Corporation of Morrow, Ga. and is marketed under the trademark Geowall.TM.. The Geowall.TM. system uses one-piece concrete panels for wall facing elements that can extend up to twenty feet in height. In order to maintain the wall facing panels in a vertically upright position, horizontally disposed polymer grid structures are securely connected to each wall facing panel, with each grid structure securely retained between layers of soil mass behind the wall face. When the grid structures are installed in the wall fill, their grid geometry interlocks with the adjacent soil to create a self-supporting, stable reinforced soil mass, thereby keeping soil pressures against the wall facing panels to a minimum. While such a prior art retaining wall system provides reinforcement to the soil fill behind the wall facing panel to (i) create a stable soil mass which stands independently of the wall facing panel, and (ii) permits the use of a variety of different facing elements, it nevertheless, suffers from several significant shortcomings and drawbacks.
In particular, since the height of the structures must equal the height of the resulting retaining wall system, heavy duty equipment is necessarily required on site for transporting and positioning of the wall facing panels into position. Also, during construction and assembly of such retaining wall systems, the wall panels must be externally braced, usually with inclined structures, which can only be removed when the wall fill behind the panels reaches two-thirds of the wall height; only until the attainment of such height, is the soil interlocked with the grid system and the retaining wall system self-supporting. Moreover, the physical connection of the grid structures to the wall panels requires "threading" each grid structure to protruding grid tabs embedded in the wall panels at time of manufacture. This threading process is both time consuming and labor intensive. Further, slack must be completely removed from the grid structures by creating pretension in the grid structure, using rakes installed in place after fill soil has been placed over the pretensioned grid structure; only thereafter, can the rakes be removed. This process is repeated for each alternating layer of soil and grid structure connected to the wall panel, until back fill soil reaches the height of the retaining wall structure.
There are, of course, several types of known retaining wall systems which are generally self-supporting.
For example, U.S. Pat. No. 4,592,678 to McNinch, Jr., et al. discloses a modular block retaining wall constructed from an ordered array of individual construction blocks. Each block has a horizontal cross-section defines a double "T" shape, where the top of the double "T" defines vertical face member and the stem of each "T" defines a generally planar leg member. Notably, elongated tension/reinforcing rods passing through vertically extending holes formed in each leg member are required in order to (i) prevent each stacked block from moving relevant to one another, (ii) achieve vertical alignment of stacked blocks, and (iii) create resistance from overturning moments. While providing a modular construction, such prior art construction blocks and retaining walls, nevertheless suffer from several significant shortcomings and drawbacks.
In particular, such prior art construction blocks cannot be "back stepped" relative to one another to form stepped retaining walls of various configuration; rather, only vertically upright retaining walls can be constructed from such construction blocks. Elongated tension/reinforcing rods must pass through each leg member to tie together a vertical array of such blocks, to prevent them from relative sliding and counteract overturning moments. Furthermore, a retaining wall system constructed from a stacked array of such blocks also requires that a concrete footing be poured under the bottom course of blocks.
Bin-type construction elements are also known for use in designing and building gravity retaining walls. Several such construction elements can be found in U.S. Pat. Nos. 3,877,236 and 4,380,409 to applicant, and 4,372,091 to Brown, et al. While these prior art construction elements have many positive features, they nevertheless have inherent drawbacks.
In particular, such construction elements are characterized by excessive weight and depth requirements. For example, these structures generally require a base that has a width of at least 50% of the desired wall height. Thus, a structure having a wall height of 20 feet would require a concrete base having a depth of 10 feet. These specific characteristics raise at least two significant problems for contractors when installing these units. One problem is the high cost of shipping such large units. The second problem is the expense associated with heavy lifting equipment required to set and place specific sized units into their desired location. In typical applications, such construction elements can weigh in excess of 10,000 pounds.
Another prior art construction element is disclosed in U.S. Pat. No. 4,684,294 to applicant and comprises an upstanding face panel arranged with a relatively long embedment beam integrally extending from the face panel in a generally T-shaped arrangement. An assembly of these construction elements are used to form a retaining wall anchored in place by the soil mass to be retained. While capable of being stacked in various configurations, such as "stacked-bonded arrays", "brick bonded patterns" and "stepped patterns", this prior art construction element has inherent drawbacks as well. For example, when forming "stepped", "stacked-bonded" or "brick-bonded" wall configurations with such construction elements, transverse support beams are required for interengaging notches formed in the embedment beam of each such construction element, in order to form a "shear key" system which prevents sliding and other movement of the assembled construction elements. Such support beams complicate retaining wall construction, and the excessive depth of the embodiment beams required for stability add to shipping and manufacturing costs.
Thus, there is clearly a great need in the construction art to provide a retaining wall construction element which can be used to construct a wide variety of retaining wall and soil reinforcement subsystems, in a simpler and easier manner.
Accordingly, it is a primary object of the present invention to provide a construction element which can be stacked and interengaged together to form a retaining wall of a variety of configurations, without the requirement of support beams used to prevent sliding and other movement of the assembled construction elements.
It is another object of the present invention to provide a retaining wall and soil reinforcement subsystem constructed from such construction elements, and which can be used to accommodate a variety of construction specifications and requirements.
It is a further object of the present invention to provide a retaining wall and soil reinforcement system of either planar-faced or stepped-back design and which does not require any additional blocks or shear keys to keep it stable.
It is an additional object of the present invention to provide a retaining wall construction element for use in conjunction with a soil reinforcement subsystem of the present invention, and which does not require attachment to the face wall of the construction element.
Another object of the present invention is to provide such construction element which is relatively lighter than prior art construction elements and thus eliminates the need for heavy lifting equipment and the high shipping costs.
An even further object of the present invention is to provide a construction element which can be used in conjunction with tie back rods to further stabilize a tall retaining wall assembled from a number of the construction elements of the present invention.
A further object of the present invention is to provide apparatus of modular design for molding retaining wall construction elements of the present invention.